Are you looking for "New" parts or used parts that are still good? Chevy's of the 40's has a lot of stuff, just not sure what your looking for.
Much of that depends on what parts you are looking for. Chevs of the 40's American classic truck parts A junk yard etc. There is no one source, some parts are harder to find than others.
I have a set of headlight buckets I would be willing to part with if you can't find them. I agree with what others have said as to suppliers. I have had good luck with Chev's of the 40's. Nice quality parts, quick shipping, helpful staff.